Regulation Of Carrier Behavior And Study Of Photoelectric Properties Based On Carbon Dots Composites

Two types of Carbon Dots(CDs)-based composites were designed for the application of carriers in the fields of photo-optic energy conversion and photo-electric energy conversion in this work.By simultaneously regulating multiple behaviors of carriers,the performance of CDs-based composites for photoluminescence,photochemical sensing and optoelectronic devices have been improved.Through the regulation of carrier behavior and systematic mechanism discussion,this work lays a theoretical foundation for the improvement of CDs-based composites properties and application in the future.1.Defects are used to stabilize unseparated carriers(excitons),and control their transportation and recombination behaviors to achieve improved photoluminescence and photochemical sensing performance.·Solid powder ultra-long room temperature phosphorescence.In this work,Zn-CDs-LDHs with controllable defects were constructed by using CDs with excellent luminescence performance as organic emitter,non noble metal zinc(Zn)as defect trigger and two-dimensional layered material hydrotalcite(LDHs)as inorganic matrix.By trapping and stabilizing triplet excitons in the composites by the defects of inorganic matrix LDHs,the transport behavior of triplet excitons from CDs to LDHs is regulated,and the radiative recombination behavior of triplet excitons to ground state is delayed.Based on the above design,a novel long-life and high-efficiency inorganic-organic composite room-temperature phosphorescent materials were obtained,with a room-temperature phosphorescence lifetime of 800 ms and an absolute phosphorescence quantum efficiency of 9.44%.·The response sensitivity of the phosphorescent composite film to oxygen is improved.On the basis of the first part of the work,this work uses Zn-CDs-LDHs with ultra-long room temperature phosphorescence lifetime as the luminescent material and polyvinyl alcohol(PVA)with abundant hydroxyl groups as the film-forming material to construct(Zn-CDs-LDHs/PVA)_n composite luminescent film.The research results show that the composite film has an ultra-long room temperature phosphorescence lifetime(1.01 s)and its phosphorescence decay intensity is linearly related to the oxygen concentration,which can be used for phosphorescence oxygen sensing.More importantly,the non-radiative recombination behavior of triplet excitons and oxygen molecules is regulated by the adsorption of oxygen through the abundant oxygen vacancies(V_O)on the surface of LDHs,which accelerates the phosphorescence quenching of the composite film.Finally,the sensitivity of the composite film to oxygen is improved.2.Rapidly separate carriers by using of macrocyclic hole materials,control their transport and recombination behaviors,and improve the performance of optoelectronic devices.In this part,a class of CDs macrocyclic hole materials with low cost,solution processability and excellent carrier separation and transport capacity were obtained by using solvothermal technology and insoluble phthalocyanine(Pc)and its derivatives as carbon sources.Perovskite solar cell(PSC)devices were constructed by compounding CDs with perovskite(PVK).The mechanism study shows that the introduction of CDs can not only quickly separate the carriers in PVK,but also transport the holes obtained after carrier separation.In addition,the appearance of new functional groups of CDs(C≡N/C=O)can effectively passivate the defects of PVK films and reduce the occurrence of carrier recombination.Based on the above designs,the power conversion efficiency of CDs-assisted PSC devices as high as 13.7%was achieved by regulating the transport and recombination behaviors of carriers in PSC devices.